Chemical nickel plating processes



United States Patent CHEMICAL NICKEL PLATING PROCESSES Application September 24, 1953, Serial No. 382,214

21 Claims. Cl. 117-50 No Drawing.

The present invention relates to improved processes of chemical nickel plating of bodies formed essentially of iron, including the various alloys thereof, i. e. steel, etc., employing baths of the nickel cation-hypophosphi-te anion type, and more particularly to such processes employing baths of the character disclosed in the copending application of Gregoire Gutzeit, Paul Talmey and Warren G. Lee, Serial No. 376,968, filed August 27, 1953.

The chemical nickel plating of a catalytic material (iron, steel, etc.) employing an aqueous bath of the nickel cation-hypophosphite anion type is based upon the catalytic reduction of nickel cations to metallic nickel and the corresponding oxidation of hypophosphite anions to phosphite anions with the evolution of hydrogen gas at the catalytic surface. The reactions take place when the body of catalytic material is immersed in the plating bath, and the exterior surface of the body is coated with nickel.

In accordance with the process disclosed in the Gutzeit, Talmey and Lee application mentioned, a plating bath is employed that consists essentially of an aqueous solution of a nickel salt and a hypophosphite and a nickel complexing agent and a separate and different exalting additive. The nickel complexing agent is selected from the group consisting of ammonia, amines, acid amines, aminocarbonyls, amine-oxides and polyalcohols, as well as saturated aliphatic hydroxycarboxylic acids, aliphatic aminocarboxylic acids and aliphatic keto acids, and the salts of these compounds. The exalting additive is selected from the group consisting of simple short chain saturated aliphatic dicarboxylic acids and aliphatic aminocarboxylic acids, and the salts of these compounds. In passing it is noted that certain of the nickel complexing agents (ammonia and amines) form molecular complexes with the nickel cations, while the remainder of the nickel complexing agents (hydroxycarboxylic acids, aminocarboxylic acids, etc.) form inner complexes or chelates with the nickel cations.

These plating baths are particularly advantageous in carrying out the chemical nickel plating process in that they exhibit very fast plating rates, and accommodate the utilization thereof in a continuous system of the character of that disclosed in the copending application of Paul Talmey and William I. Crehan, Serial No. 222,- 222, filed April 21, 1951, now Patent No. 2,658,839, granted November 10, 1953, wherein the plating bath is recirculated between a plating chamber and a reservoir with the build-up of phosphite anions therein to a concentration in excess of one molar, Without the precipitation of nickel phosphite and mixed basic salts.

In fact these plating baths exhibit normal plating rates in excess of 1 mil (0.001) per hour at optimum pH, above about 5.5, the higher pH favorably influencing the plating rate.

However, it has now been discovered that the chemical nickel plating process disclosed in the Gutzeit, Talmey and Lee application, when these plating baths of the higher pH are employed, is productive of nickel coatings upon bodies formed essentially of iron, i. e., steel, etc., that are not quite as adherent as is desirable, particularly when the plated bodies are subjected to repeated strains in their subsequent use.

Also, it has been discovered that the resistance of these nickel coatings to electrolytic corrosion, as ex-.

hibited by salt spray tests, is dependent upon thehomogeneity of the surface of the body, as influenced by the preparation or pretreatment thereof preceding the chemical nickel plating operation; and more specifically, it has been discovered that the resistance to electrolytic corrosion is more or less directly proportional to the homogeneity of the surface of the body, the more nearly homogeneous the surface of the body, the higher the resistance of the subsequently produced nickel coating is to electrolytic corrosion.

Accordingly, it is a general object of the present invention to provide an improved process of chemical nickel plating of bodies formed essentially of iron, employing plating baths of the nickel cation-hypophosphite anion type, that is productive of very adherent nickel coatings and that also exhibit great resistance to electrolytic corrosion.

Another object of the invention is to provide an im proved process of producing a nickel coating of substantial thickness upon the surface of a body formed essentially of iron, employing chemical nickel plating, wherein the nickel coating possesses great adhesion, exhibits great resistance to flaking incident to strains of the body, and possesses high corrosion resistance.

A further object of the invention is to provide an improved process of pretreating a body formed essentially of iron, before chemical nickel plating of the body, whereby the subsequent chemical nickel plating of the body is productive of a superior nickel coating thereon.

These and other objects and advantages of the invention pertain to the particular arrangement of the steps of the process, as will be understood from the foregoing and following description.

In accordance with the process of the present invention, the article or body to be nickel plated and formed essentially of iron, including the various alloys thereof, i. e. steel, etc., is first subjected to a composite pretreatment, the following having been found to be highly successful:

1. The body is subjected to a conventional vapor degreasing step.

2. The body is then subjected to a conventional alkaline cleaning step at a temperature of about 180 F. for a time interval of about 5 to 20 minutes.

3. The body is then subjected to a rinsing step in water at a temperature of about F. for'a time interval of about 5 minutes.

4. The body is then subjected to a pickling step in an aqueous solution of hydrochloric acid at room temperature (about 70 F.) for a time interval of about 4 minutes, the solution containing about 15% HCl by weight.

5. The body is subjected to a repetition of step'No. 3 above.

6. The body is subjected to a repetition of step No. 2 above.

7. The body is subjected to a repetition of step No. 3 above.

8. The body is subjected to a repetition of step No. 4 above.

9. The 'body is then subjected to a rinsing or soaking step in an aqueous solution of hydrogen peroxide at a temperature of about 110 F. for a time interval of about 5 minutes, the solution containing not in excess of about 0.1% of hydrogen peroxide by weight.

.sulting from step No.9, set forth above. this composite pretreatment positively insures cleaning and degrea'sing'of the surface of the body, as well as the film possibly being afil'rn of Fes04.

in this composite pretreatment, inclusion of steps Nos. t0 8, inclusive, set forth above, being repetitiousofcertain of the preceding steps, is optional, but preferably thesefsteps are included as amatter of precaution, so as positively to insure'that the surface of thefbody is in readiness to receive'the'very thin'irou oxide film thereon, re-

Accordingly,

formation of the very thin iron oxide film thereon,'without the formation of'any visible'rust thereon; whereby the surface of thebody is made substantially homogeneous and lightly oxidized as noted above, the iron oxide This homogeneity of the'surface of the body brings about the subsequent production of a more homo eneous nickel coating thereon,

thus preventing local. galvanic action and electrolytic corrosion of, the nickel t coating and improving'the corrosion resistance "of'thehickel coating tosalt'spray tests.

.After the body vhas been subjected to the composite pretreatmentdescribed"above, it'isimmersed in a hot strike bath consisting essentially of an aqueous solution of a nickel salt, and having a temperature slightly below the boiling point thereof, about 210 F.,"and having a pH in the approximate'range'of "119 to 3.5. More particularly, the body is immersed in the -strike solution-for a first time interval in excess of 3 minutes, up to about minutes, that is sufliciently long'to effect a displacement reaction resulting in thedeposit of a thin nickel film upon the surface'of the body in accordance with theequation:

This displacement reaction (1) proceeds only until the surface-of the body'is coated with a thinlayer of nickel, and is substantially of monomolecularthickness;

and preferably, the strike oath has a pH within the range 2.2 to 3.0.

7 After the body has been subjected to the nickel strike bath described above,-it is immersed-in a hotplating bath consisting essentially of anaqueous solution of a nickel 1 salt land a 'hypophosphite, and "having a temperature slightly below the boiling pointthereof, about 210 'F.,

This catalyticreaction (2) proceeds uponanautocatalytic basis so that the composite nickel coating upon the surface of the body may be built .up to the desired thickness.

After. the body has been subjected to the nickel-plating bath described above, it isrinsed and is ready for use, the nickel coating thereon being firmly adhered'thereto and exhibiting great resistance to flaking, particularly when the plated body is subjected to repeated strains in its subsequent use.

In passing, it is noted that there exist several methods for determining, in a more or less qualitative manner, the adhesion of a nickel coating or plating on a base metal; and specificallyit has been found that a very satisfactory and simple procedure resides in: first providing an elongated steel strap having a thickness of about A and a width of about to 1%", the midportion of the strap being necked down about A along each edge thereof for a distance of at least 2"; then plating the steel strap in the manner previously described; then subjecting the plated steel strap to a tension breaking test;and then examining the raw broken-edges of the two portions of the steel strap in order to determine'the amountofflaking of the nickel coating adjacent to the break. Specifian appropriate time interval.

cally, it has been discovered that in the event no flaking ofthe nickel deposit occurs further back than from the break, the nickel coating possesses great adhesion and is not flaked by various other tests, including impact, compression, torsion, etc., tests. Accordingly, hereinafter in the testing of a sample in accordance with the procedure above-outlined: when the flaking of the nickel deposit back from thebreak is A the nickel coating is considered to be good.; when the flaking of the nickel deposit back from the break is greater than 5 the nickel coating is considered to be poor; and when the-flaking of the nickel deposit back from'the break is less than $5 the nickel coating is considered to be excelleu While it is appreciated that this standard is empirical, it is exceedingly useful, as a nickel coating that has been found to'be good in accordance withthissimple test, exhibits in other more complex tests great adhesion to the base metal.

In order to demonstrate the processof the present invention, an aqueous strike bath was prepared that "had the following composition: Strike bath SBl:

Nickel chloride m. p. l 0.0675

Sodium succinate m.,p. l 0.06 pH adjusted with NaOH and HCl.

Also, an aqueous platingbath was prepared that had the following composition:

Plating bath PBl:

Malic acid -m. p. I 0.135 Aminoacetic acid m.-p. 1. 0.0675 Nickel chloride m. p. 1. 0.0675

Sodium hypophosphite m. p. l. 0.225 2.p..p. m. Pb++ added as stabilizing ion. pH adjusted with NaOH and HCl.

Samples of cold rolled steel, eaChhaving an area of -85 cm. ,'were subjected to the composite pretreatment hereinbefore described, then rinsed .in hot water, then immersed in the strike bath SBl for a time interval of '3 minutes, and then immersedin the plating bathPBl for In this series of tests, the pH of the strike bath SBl was varied, as indicated below; while the pH of the'plating'bath PBl was established in the vicinityof 6.0, since'this plating bath exhibits a plating rate greater than 1.1 mils per hour at this pH. The results of these tests were as follows:

, Initial pH Time of Mils pH of Strike Bath SBl of Plating Plating Plated Adhesion Bath PB1 (mins) 6 20 3. 76 poor.

6 20 90 3.20 very good. 6 30 3. 00 Do.

6. 30 110 3.- 80 fair.

6. 30 110. 3. 36 poor.

The foregoing tests clearly demonstrate that in the present process, the pH of the strike bath SBl should be in the approximate range 1.9 to 3.5,and preferably within the narrower range 2.2 to 3.0, in order to obtain maximum adhesion of'the nickel coating upon the base metal sample.

In a number of subsequent tests, a number of other aqueous strike baths were prepared that had the compositions indicated below:

Strike bath SBS: Plating bath PB6: v Nickel chloride m. p. 1.... 0.0675 Nickel chloride m. p. 1 0.0675 Acetic acid m. p. l 0.06 Sodium hypophosphite m. p. l

. Sodium succinate m. p.

Stnke P 1 0675 5 Malic acid m. p. l 0.06 NlckFl 06 Lactic acid m. p. 1 0.2025 Lactlc and t Pb++ stabilizing ion p. p. m 2

Strike bath SB7: Plating bath PB7:

N1clelchlor1de P- Q0675 Nickel chloride m. p. 1 0.0575 m suwpate Q06 Sodium hypophosphite m. p. 1 0.225 Sodmm fluonde P- Malic acid m. p. 1 0.0675

Strike bath Aminoacetic acid m. p. 1 0.0675 Nicke chlorlde m. p. 1 0.0575 Pb++ stablhzmg 1011 --P- P- 2 Aminoacetic acid m. p. 1 0.0675 Additional samples of cold rolled steel, each having an 15 area of 80-85 cm. were subjected to the composite prei gig ho bite m P 1 006 treatment hereinbefore described; then rinsed in hot Mano 5; p Sp 0 water; then immersed in one of the strike baths SB2 to 5 0 6 S312 for a time interval of 3 minutes, and then immersed '7" u in one of the plating baths PBZ to PB7, for an appropriate Strike bath S310: time interval. In this series of tests, the pH of the various Nickel chloride m. p. 1 0.0675 strike baths were varied, as indicated below; while the pH Sodium succinate m. p. l 0.06 of the various plating baths were selected substantially Malic acid m. p. l 0.06 at the highest plating rate thereof. Illustrative results of Lactic acid m. p. 1 0.2025 this series of tests were as follows:

pH of Plating Initial Time of Time of Strike Strike Bath pH of Strike Plating Mils Adhesion Bath No. Bath No. Plating (Min.) (Min) Plated Bath 2.30 P132 5. 60 3 110 2.89 good. 2.30 P152 5.60 4 135 3.19 very good. 2. P32 5.60 5 115 1.89 excellent. 2.30 PB2 5.50 5 115 1.94 o. 2. 25 PB3 5.70 5 108 2.01 very good. 2.15 PB3 5.70 a 120 2.05 fair. 2.30 PB3 6.30 5 115 2.71 verygood. 2.30 P33 6.00 5 65 1.95 Do. 0.50 PB2 5. 2 115 1.85 poor. 3.0 PBS 5.50 2 140 2.41 good.

Strike 1 3 5311; These plating tests again illustrate that the pH of the Ni k l hl id 1 0.0675 strike bath should be in the approximate range 1.9 to 3.5, Sodium succinate m. p. l 0.12 40 and urth r demonstrate that the time of nickel strike is Malic acid m. p. l 0.06 considerably reduced in the strike baths that also contain certain of the organic additives.

Smke P i fl 00675 -In a modified form of the present process, the body ig 6 6 termed essentially of iron, after being subjected to the M .g zi 'gggfi 0 (i675 pretreatment previously described, is immersed in a hot Also, a number of other aqueous plating baths were prepared that had the compositions indicated below:

Plating bath PBZ:

Nickel chloride m. p. 1 0.0675 Sodium hypophosphite m. p. 1 0.225 Sodium succinate m. p. l 0.06 Malic acid m. p. 1 0.2025 Pb++ stabilizing ion p. p. m-.. 2 Plating Bath PB3:

Nickel chloride m. p. 1 0.0675 Sodium hypophosphite m. p. 1 0.225 Malic acid m. p. 1 0.2025 Amiuoacetic acid m. p. 1 0.0675 Pb++ stabilizing ion p. p. m 2 Plating bath PB4: I

Nickel chloride m. p. 1 0.0675 Sodium hypophosphite m. p. 1 0.225 Sodium succinate m. p. l 0.20 Malic acid m. p. l 0.06 Lactic acid m. p. 1 0.2025 Pb++ stabilizing ion p. p. m 2 Plating bath PBS Nickel chloride m. p. 1 0.0675 Sodium hypophosphite m. p. l 0.225 Sodium succinate m. p. l 0.16 Malic acid m. p. l 0.06 Lactic acid m. p. 1 0.2025 Pb++ stabilizing ion p. p. 111-- 2 bath of the plating type described, but having a relatively low pH of a value of around 4.5, for a time interval of 10 to 20 minutes; then the pH of the plating :bath is increased stepwise to a value above about-'5.5 :by the corresponding additions thereto of a soluble alkali, such as caustic soda; and then the plating is continued at the relatively high pH for the required time interval to obtain the desired thickness of the nickel coating.

In order to demonstrate this modification of the present process a cold rolled steel sample of cm. area was first subjected to the composite pretreatment previously described; and a plating bath of 6 liters was prepared that had the following composition:

This plating bath was divided into three equal parts of 2 liters each, and the pH was adjusted with NaOH and HCl as follows:

Part l2 liters 4.50 pH Part 22 liters 5.20 pH Part 3-2 liters 6.20 pH The previously prepared steel sample was placed in the plating chamber of the continuous plating system of the character disclosed in the previously mentioned Talmey and Crehan application; and then the first, sec- 0nd and third portions of this plating bath were suc- 7 cessively flowed through the plating chamber-at a temperature. of about 210 F., during. a, total time interval of. 120 minutes, The weightgain'of this steel sample was 3.7 grams; the nickel deposit had a thickness of 2.1'mils; and the adhesion. of the nickelcoating 'was excellent- In passing, it isnoted that. inv this modificationzo'f the present process, it is important to raise thepH of the plating bath gradually in order to obtain good adhesion of the nickel coating upon the base metal formedzessentially ofiron.

In another modified form of the present process, substantially identical to that described above, the body formed essentially of iron, after being subjected to the composite pretreatment, previously described, is immersed in a hot bath of the strike type described consisting essentially of an aqueous acid solution of a nickel salt; and after the nickel strike upon the surface of the body, "the strike bath is converted into a bath. of the plating type described stepwise by the corresponding additions thereto of both a soluble 'hypophosp'hite and a soluble alkali, such as sodium hypophosphite and caustic soda; and in this modification of the present process, it is immaterial Whether the various soluble organic additives are initially placed in the strike bath or are added thereto incident to the conversion of the strike bath into the plating bath.

In a further modified form of the present process, the body formed essentially of iron, is first subjected to the composite pretreatment previously described, and is then immersed in a cool bath of the plating type described at a temperature in the approximate range 130 F. to 150 F. for a time interval of about 10 to 20 minutes; and then the temperature of the plating bath is increased gradually to a temperature slighly below the boiling point thereof, about 210 F. In this modification of the present process, the initial nickel strike upon the surface of the body takes place very slowly in the relatively cool plating bath; and thereafter, the catalytic nickel plating and build-up of the nickel coating take place as time proceeds in the relatively hot plating bath.

In the formation of aqueous plating baths of the type disclosed in the Gutzeit, Talmeyand Lee application mentioned, the soluble nickel salt may takea variety of forms, such, for example, as nickel chloride, nickel sulfate, etc., or mixtures thereof; and the soluble hypophosphite may take a variety of forms, such, for example, as sodium hypophosphite, potassium 'hypophosp'hite, calcium hypophosphite, etc., or mixtures thereof. In the plating bath, the absolute concentration of hypophosphite ions is in. the approximate range 0.15 to 1.20 mole/liter, and the ratio between nickel ions and hypophosphite ions is in the approximate range 0.25to =1 .60.

A typical malic acid-lactic acid-succinate plating bath of this type further comprises an absolute concentration of malic acid ions in the approximate range 0.04 to 0.20 mole/liter; an absolute concentration of lactic acid ions in the approximate range 0.04 to 0.20 mole/liter; the total quantity of the malic acid ions and the lactic acid ions are suficientto complex at least 100% of thenickel ions; an absolute concentration of succinic acid ions of at least 0.04 mole/liter; and a pH within the approximate range 4.5 to 7.0.

A typical malic acid-glycine plating bath of this type further comprises an absolute concentration of malic acid ions sufficient to complex at least 100% of the nickel ions; an absolute concentration of glycine ions 'of at least 0.04 mole/liter; and a pH within the approximate range 4.5 to 9.5.

A typical malic acid-succinate plating bath of this type further comprises an absolute concentration of malic acid ions sufiicient to complex at least 100% of the nickel ions; an absolute concentrate of succinic acid. ions, of at least 0.04 mole/liter; anda pH within the approximate range 4.5 to 7.0. 1

These plating baths of. the type described are particularly well suited for use in a continuous plating system of the character noted, as they exhibit a fast plating; rate, have. an exceedingly long life, and maintain nickel phosphite in solution in concentrations as high as one molar. Moreover, when these plating baths are employed in the present process, the nickel coatings upon bodies formed essentially of iron, including the various alloys thereof, i. e. steel, etc., are exceedingly adherent, homogeneous, smooth and bright.

In view of the foregoing,. it is apparent mat there has been provided an improved process. of chemical nickel plating of bodies formed essentially of iron, including the various alloys thereof, i. e. steel, etc., that is productive of exceedingly adherent nickel coatings having high resistance to electrolytic corrosion whereby the process is particularly well suited to the chemical nickel plating of forged and cast steel elements and parts.

Whilethere has been. described. what is at present considered to be thepreferredembodiment of the invention, it will be understood. that various modificationsmay be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. The process of'producing a nickel coating of substantial thickness upon the surface of a body formed essentially of iron, which comprises cleaning and degreasing the surface of said body, contacting said body with an aqueous solution of hydrogen peroxide for a time interval sufficiently long to form only a thin iron oxide film upon the surface of said body and without the formation of any visible rust upon the surface thereof, said solution containing. not in excess of about 0.1% by weight of hydrogen peroxide, then contacting said body with a first hot nickel plating bath comprising an aqueous solution of a nickel salt and having a temperature slightly below the boiling point thereof and having a pH in the approximate 7 range 1.9 to 3.5 during a first time interval sufliciently long to effect the displacement deposit of a thin nickel film. upon the surface of said body, and then contacting said body with'a second 'hot nickel plating bath comprising an aqueous solution of a'nicke'l salt and a hypophos'phite and having a temperature slightly below the boiling point thereof and having a pH in the approximate range 4.0 to 9.5 during a. second time intervalsufficientlyilong to elfect the catalytieplating of. additional nickel upon. said thin ni'ckelfilrn: and; the. buildup of. a composite nickel coating of substantial thickness upon the surface of said body.

2. The'pro'cess of producing a nickel coating of substantial thickness upon the surface ofa body formed essentially of iron, which comprises cleaning and degreasing the surface of said body, rinsingthe surface of said body' in anaqueous solution of hydrogen peroxide to form a thiniron-oxide-filmupon the surface thereof and without the formation of any visible rust upon the surface thereof,said solutioncontaining not in excess of about 0.1% by weight of hydrogen peroxide, then contacting said body withafirsthotnickel plating. bath comprising an aqueous solution. of a. nickel salt and having a temperature. slightly below the boiling point thereof and having a pH. in the. approximate range 1.9 to 3.5 during a first time interval. sufliciently long to effect the displacement deposit of a thin nickel film upon the surface of said body, and then contacting said body with a second hot nickel plating bathcomprising an aqueous solution of a nickel salt. and a hypophosphite and having a' temperature slightly below the boiling point 7 thereof and having a pI-Iinthe approximate range 4.0 to 9.5 during'a second time interval sufficiently long to effect the catalytic plating of additional nickel upon said thin nickel film and build-up of a composite nickel coating of substantial for a time interval sufiiciently long to form only a thin iron oxide film upon the surface of said body and without the formation of any visible rust upon the surface thereof, said solution containing not in excess of about 0.1% by weight of hydrogen peroxide, and then contacting said body with a nickel plating bath comprising an aqueous acid solution of a nickel salt and having a pH in the approximate range 2.2 to 3.0 in order to effect the displacement deposit of a thin nickel film upon the surface of said body.

4. The process of plating with nickel the surface of a body formed essentially of iron, which comprises cleaning and degreasing the surface of said body, soaking said body in an aqueous solution of hydrogen peroxide for a time interval sufficiently long to form only a thin iron oxide film upon the surface thereof and without the formation of any visible rust upon the surface thereof, said solution containing not in excess of about 0.1% .by weight of hydrogen peroxide, and then contacting said body with a nickel plating bath of an aqueous solution of a nickel salt in order to effect the displacement deposit of a thin nickel film upon the surface of said body.

5. The process of producing a nickel coating of substantial thickness upon the surface of a body formed essentially of iron, which comprises cleaning and degreasing the surface of said body, contacting said body with an aqueous solution of hydrogen peroxide for a time interval sufficiently long to form only a thin iron oxide film upon the sufiace thereof and without the formation of any visible rust upon the surface therof, said solution containing not in excess of about 0.1% by weight of hydrogen peroxide, contacting said body with a first nickel plating bath comprising an aqueous solution ofa nickel salt and having a pH in the approximate range 1.9 to 3.5 during a first time interval sufficiently long to effect the displacement deposit of a thin nickel film upon the surface of said body, and then contacting said body with a second nickel plating bath comprising an aqeuous solution of a nickel salt and a hypophosphite and having a pH in the approximate range 4.0 to 9.5 during a second time interval sufficiently long to effect the catalytic plating of additional nickel upon said thin nickel film and build-up of a composite nickel coating of substantial thickness upon th surface of said body. i

6. The process set forth in claim 5, wherein said first and second nickel plating baths have temperatures slightly below the boiling points thereof and said first time interval is in the approximate range 3 to 10 minutes and said second time interval is at least 60 minutes.

7. The process of producing a nickel coating of substantial thickness upon the surface of a body formed essentially of iron, which comprises cleaning and degreasing the surface of said body, contacting said body with an aqueous solution of hydrogen peroxide for a time interval sufiiciently long to form only a thin iron oxide film upon the surface of said body and without the formation of any visible rust upon the surface thereof, said solution containing not in excess of 0.1% by weight of hydrogen peroxide, contacting said body with a first nickel plating bath comprising an aqueous solution of a nickel salt and having a pH in the approximate range 2.2 to 3.0 during a first time interval sufficiently long to effect the displacement deposit of a thin nickel film upon the surface of said body, and then contacting said body with a second nickel plating bath comprising an aqueous solution of a nickel salt and a hypophosphite and having a pH in the approximate range 4.0 to 9.5 during a second time interval sufiiciently long to effect the catalytic plating of additional nickel upon said thin nickel film and the build-up of a complete nickel coating of substantial thickness upon the surface of said body.

8. The process of producing a nickel coating of substantial thickness upon the surface of a body formed essentially of iron, which comprises cleaning and degreasing the surface of said body with an aqueous solution of hydrogen peroxide for a time interval sufficiently long to form only a thin iron oxide film upon the surface thereof and without the formation of any visible rust upon the surface thereof, said solution containing not in excess of about 1.0% by weight of hydrogen peroxide, contacting said body with a first nickel plating bath comprising an aqueous solution of a nickel salt and also containing an additive selected from the group consisting of short chain saturated aliphatic carboxylic acids and alkaline salts thereof and having a pH in the approximate range 1.9 to 3.5 during a first time interval sufficiently long to eflect the displacement deposit of a thin nickel film upon the surface of said body, and then contacting said body with a second nickel plating bath comprising an aqueous solution of a nickel salt and a hypophosphite and also containing an additive selected from the group consisting of short chain saturated aliphatic carboxylic acids and alkaline salts thereof and having a pH in the approximate range 5.5 to 9.5 during a second time interval sufiiciently long to effect the catalytic plating of additional nickel upon said thin nickel film and the build-up of a composite nickel coating of substantial thickness upon the surface of said body.

9. The process of producing a nickel coating of substantial thickness upon the surface of a body formed essentially of iron, which comprises cleaning and degreasing the surface of said body, contacting said body with an aqueous solution of hydrogen peroxide for a time interval sufiiciently long to form only a thin iron oxide film upon the surface thereof and without the formation of any visible rust upon the surface thereof, said solution containing not in excess of about 0.1% by weight of h drogen peroxide, providing a first nickel plating bath comprising an aqueous solution of a nickel salt and having a pH in the approximate range 1.9 to 3.5, providing a second nickel plating bath comprising an aqueous solution of a nickel salt and a hypophosphite and having a pH in the approximate range 4.0 to 9.5 immersing said body in said first nickel plating bath to effect the displacement deposit of a thin nickel film upon the surface thereof, withdrawing said body from said first nickel plating bath and immersing it in the said second nickel plating bath to effect the catalytic plating of additional nickel upon said thin nickel film and the build-up of a composite nickel coating upon the surface of said body, and withdrawing said body from said second nickel plating bath when the composite nickel coating upon the surface thereof has reached the substantial thickness desired.

10. The process of producing a nickel coating of substantial thickness upon the surface of a body formed essentially of iron, which comprises cleaning and degreasing the surface of said body, contacting said body with an aqueous solution of hydrogen peroxide for a time interval sufiiciently long to form only a thin iron oxide film upon the surface thereof and Without the formation of any visible rust upon the surface thereof, said solution containing not in excess of about 0.1% by weight of hydrogen peroxide, providing a first nickel plating bath comprising an aqueous solution of a nickel salt and having a pH in the approximate range 1.9 to 3.5, providing a second nickel plating bath comprising an aqueous solution of a nickel salt and a hypophosphite and having a pH in the approximate range 4.0 to 9.5, immersing said body in said first nickel plating bath to initiate the displacement deposit of nickel upon the surface thereof, withdrawing said body from said first nickel plating bath after a time interval sufficiently long to effect the displacement plating of a thin nickel film upon the surface thereof, immersing said body in said second nickel plating bath to initiate the catalytic plating of additional nickel upon said thin nickel film and the build-up of a composite nickel coating upon the surface of said body, and withdrawing said body from said second nickel plating bath when the composite nickel coating upon the surface thereof has reached the substantial thickness desired.

11. The process of producing a nickel coating of sub-v stantial thickness upon the surface ofa body formed essenv tially of iron, which comprises cleaning and degreasing the surface of said body, contacting said body with an aqueous solution of hydrogen peroxide for a time interval sufiiciently long to form only a thin iron oxide film upon the surface thereof and without the formation of any visible rust upon the surface thereof, said solution containing bath of both a soluble hypophosphite and a soluble alkali so that the pH of said second nickel plating bath is brought up into the approximate range '4.0 to.9.5 in order to initiate the catalytic plating of additional nickel upon said thin nickel 'film and the build-up of a composite nickel coating upon the surface of said body, and withdrawing said body from said'second nickel plating bath when the composite nickel coating upon the surface thereof has reached the substantial thickness desired.

12. The process set forth in claim 11, wherein said conversion of said first nickel plating bath into said seco'nd nickel plating bath is made in a number of steps bythe additions at a corresponding number of spacedtime intervals of appropriate small-quantities of said soluble hypo phosphite and said soluble alkali to said first nickel plating bath. 7

13. The process of producing a nickel coating of substantial thickness upon the surface of a body formed-essentially of iron, which comprises cleaning and degreasing the surface of said body with an aqueous solution of hydrogen peroxide for a time interval sufiicientl'y long to form only a thin iron oxide film upon the surface thereof and without the formation of any visiblerust upon the surface thereof, said solution containing not in excess of about 0.1% by weight of hydrogen peroxide, providing a first nickel plating bath comprising an aqueous solution of a nickel salt and also containing an addifive selected from the group consisting of short chain saturated aliphatic carboxylic acids and alkaline salts thereof and having a pH in theapproximate range L9 to 3.5, immersing said body in said first nickel plating bath to initiate the displacement deposit of nickel upon the surface thereof, converting said first nickel plating bath into a second nickel plating bath after a time interval sufiiciently long to effect the displacement deposit of a thin nickelfilm upon the surface of said body by the addition to said first nickel plating bath of both a soluble hypophosphite and a soluble alkali so that the pH of said second nickel plating bath is brought up into the approximate range 4.0 to 9.5 in order to initiate the catalytic plating of additional nickel upon said thin nickel film and the build-up of a composite nickel coating upon the surface of said body, and withdrawing said body from said second nickel plating bath when the composite nickel coating upon the surface thereof has reached the substantial thickness desired. I

14. The process of producing a nickel coating of substantial thickness upon the surface of a body formed essentially of iron, which comprises cleaning and degreasing the surface of said body, contacting said body with an aqueous solution of hydrogen peroxide for a time interval sufficiently long to form only a thin iron oxide film upon the surface thereof and without the formation of any visible rust upon the surface-thereof, said solution containing not in excess. of about 0.1% by. weight of hydrogen peroxide, providing a first nickel plating bath comprising an aqueous solutionof a nickel salt and a I posite nickel coating upon the surface of said body, and withdrawing said body from said second nickel plating hypophosphite and having a'pH in theapproximate range 1.9 to 3.5, immersing said body in said first nickel plating bath to initiate the displacement deposit of nickel upon the surface thereof, converting said first nickel plating bath into a second nickel plating bath after a time interval sufiiciently long to effect the displacement deposit of a thin nickel film upon the surface of said body by the addition to said first nickel plating bath of a soluble alkali so that the pH of said second nickel plating bath is brought up into the approximate range 4.0 .to 9.5 in order to effect the catalytic plating of additional nickel upon said thin nickel film and the build-up of a combath when the composite nickel coating upon the surface thereof has reached the substantial thickness desired.

15. The process set forth in claim 14, wherein said conversion of said first nickel plating bath into said second nickel plating bath is made in a number of steps by the additions at a corresponding number of spaced time intervals of appropriate small quantities of said soluble alkali to said first nickel platin'gba'th.- I

l6.'The process of producing anickel coatingof substantial thickness upon the surface of a body formed essenaqueous solution of hydrogen peroxide for a time interval sufiiciently long to form only a thin iron oxide film upon the surface thereof and without the formation of any visible rust upon the surface thereof, said solution containing not in excess of 0.1% by weight of hydrogen peroxide, providing a "first nickel plating bath comprising an aqueous solution of a nickel salt and a hypophosphitc and also containing a'n' additive selected from the group consisting. or short chain saturated aliphatic carboxylic acids and alkaline salts thereof and having a pH in the approximate range 1.9 to 3.5, immersing said body in said first nickellpl'ating' bath' to initiate the displacement deposit of nickel upon the surfacethereof, converting said first nickel plating bath". into a second nickel plating bath after a time interval sufficiently long to effect the displacement deposit of a thin nickel filin upon the surface of said body by the additior'i'to said first nickel'plating bath of a soluble alkali so that the pH of said second nickel plating bath is brought up into the approximate range 4.0 to 9;5-'in order to eifect the catalytic plating of additional nickel upon' said thin nickel film and-the build-up of a-composite nickel coating upon the surface of said body, and withdrawing said body from said second nickel. plating bath when the composite nickel coating upon-the surface thereof has reached'the substantial thickness desired;

17. The process of producingya' nickel coatingzof-subs'tantial thickness upon the surface of a' body formed essentially of iron, which comprises cleaninganddegr'easing the surface or said body, rinsing the surface of said body in an aqueous solution-of hydrogen peroxide to form a thin iron oxide film upon "thesurface thereof and without the formation of any visible rust upon the surface thereof, said solutioncontaining not in excess of about 0.1% by weightof hydrogen-peroxide, providing a nickel plating =bath'- comprising; anaqueoussolution of a nickel salt' and a hypophosphite and having atemperature slightly below the boilingxpoint thereof, andimmersing said body in said nickelflplating bath during a time interval sufiiciently long to effect plating of a nickel coating ofysub stantial thickness upon the surface'of said body.

18. The process set forth in claim; 17-, wherein said nickel plating bathhas a pH- in the approximate range 5.5 to 9.5. I V t 19. The process of producing a nickel coating of substantial thickness upon-the surface [of a body formed essentially ofiron, which-comprises cleaning and degreesingof th'esurface ofsaid b ody,.for'ming a thin iron oxide film'up'on the surface ofsaid body and without the formation of any visible rust upon the surface thereof by soaking said body in a warm aqueous solution of hydrogen peroxide, said solution having a temperature of about 110 F. and containing not in excess of about 0.1% by weight of hydrogen peroxide, providing a nickel plating bath comprising an aqueous solution of a nickel salt and a hypophosphite and also containing an additive selected from the group consisting of short chain saturated aliphatic carboxylic acids and alkaline salts thereof and having a pH in the approximate range 5.5 to 9.5, and immersing said body in said nickel plating bath during a time interval sufliciently long to effect plating of a nickel coating of substantial thickness upon the surface of said body.

20. The process of producing a nickel coating of substantial thickness upon the surface of a body formed essentially of iron, which comprises cleaning and degreasing the surface of said body, forming a thin iron oxide film upon the surface of said body and without the formation of any visible rust upon the surface thereof by soaking said body in an aqueous solution of hydrogen peroxide, said solution containing not in excess of about 0.1% by weight of hydrogen peroxide, immersing said body in a cool nickel plating bath comprising an aqueous solution of a nickel salt and a hypophosphite, said nickel plating bath having a temperature well below the boiling point thereof, increasing the temperature of said nickel plating bath to a temperature slightly below the boiling point thereof, and withdrawing said body from said hot nickel plating bath after a time interval sufiiciently long to effect plating of a nickel coating of substantial thickness upon the surface of said body.

21. The process of producing a nickel plating of substantial thickness upon the surface of a body formed essentially of iron, which comprises cleaning and degreasing the surface of said body, forming a thin iron oxide film upon the surface of said body and without the formation of any visible rust upon the surface thereof by soaking said body in an aqueous solution of hydrogen peroxide, said solution containing not in excess of about 0.1% by weight of hydrogen peroxide, providing a cool nickel plating bath comprising an aqueous solution of a nickel salt and a hypophosphite and also containing an additive selected from the group consisting of short chain saturated aliphatic carboxylic acids and alkaline salts thereof and having a pH in the approximate range 5.5 to 9.5, said nickel plating bath having a temperature well above the boiling point thereof, immersing said body in said cool nickel plating bath, increasing the temperature of said nickel plating bath to a temperature slightly below the boiling point thereof, and withdrawing said body from said hot nickel plating bath after a time interval sufiiciently long to eifect plating of a nickel coating of substantial thickness upon the surface of said body.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain Mar. 23, 

4. THE PROCESS OF PLATING WITH NICKEL THE SURFACE OF A BODY FORMED ESSENTIALLY OF IRON, WHICH COMPRISES CLEANING AND DEGREASING THE SURFACE OF SAID BODY, SOAKING SAID BODY IN AN AQUEOUS SOLUTION OF HYDROGEN PEROXIDE FOR A TIME INTERVAL SUFFICIENTLY LONG TO FORM ONLY A THIN IRON OXIDE FILM UPON THE SURFACE THEREOF AND WITHOUT THE FORMATION OF ANY VISIBLE RUST UPON THE SURFACE THEREOF, SAID SOLUTION CONTAINING NOT IN EXCESS OF ABOUT 0.1% BY WEIGHT OF HYDROGEN PEROXIDE, AND THEN CONTACTING SAID BODY WITH A NICKEL PLATING BATH OF AN AQUEOUS SOLUTION OF A NICKEL SALT IN ORDER TO EFFECT THE DISPLACEMENT DEPOSIT OF A THIN NICKEL FILM UPON THE SURFACE OF SAID BODY. 